Geoffrey of Monmouth was born around 1100 CE, it is not certain that he was
born in Monmouth in South East Wales
but it is likely that as he took his name from the area, he was born there.

His father was named Arthur. Geoffrey was
appointed archdeacon of Llandaff in 1140 and was
consecrated bishop of St. Asaph in 1152. He died c.
1155.

Geoffrey is one of the most significant authors in the development of the
Arthurian legends. It was Geoffrey who, in his HistoriaRegumBritanniae
(completed in 1136) palces Arthur in† a historical context and in the line
of British kings as a pre- Saxon ruler.

This work not only established Arthur as a
significant historical figure but also gave him an authoritative history which
included many events familiar from later romance. Geoffrey also introduced the
character of Merlin as we know him into the legends. Geoffrey's Merlin, a
combination of the young and prophetic Ambrosius in Nennius's history and the prophet Myrddin
who figures in several Welsh poems, first appears in a book known as the ProphetiaeMerlini
(The Prophecies of Merlin), which was written about 1135 but then
incorporated as Book VII of the Historia.

This book contains the prophecies made by
Merlin to the earlier celtic ruler Vortigern, which foreshadow not only the downfall of Vortigern but also the rise and fall of Arthur, events
subsequent to the end of the Historia, and
events of the obscure future.

The Historia proper begins in the legendary
past and traces the origin of Britain
to its eponymous founder Brut, the great-grandson of Aeneas. (Because of this
purported origin, histories of Britain
were known as "Bruts.") Subsequent chapters
tell of legendary and actual events in British history, including the story of
Lear and his daughters, the offer of tribute from Rome to Belinus
and Brennius, Julius Caesar's unsuccessful attempt at
conquest, and the disasterous invitation of the
Saxons to Britain by Vortigern.

The Arthurian portion of the story tells of Arthur's conquests on the
continent, his slaying of the giant of St. Michael's Mount, a prominent role by
Gawain in the Roman wars, the slaying of the Emperor Lucius,
the treachery of Mordred, the entry of the nunnery by
Guinevere, and the final battle between Mordred, who
is killed, and Arthur, who is borne to the Isle of Avallon
for the healing of his wounds.

The influence of† theHistoria on literature is enormous. It influenced
numerous vernacular works, including translations into Welsh, Old Norse, and
the French and English verse versions by Wace (the Roman
de Brut) and Layamon (the Brut).

Geoffrey also wrote a Vita Merlini (Life of
Merlin) in verse in about 1150.